Soil-applied pre-plant incorporated and pre-emergence herbicides play an important role in the early control of weeds which in turn determine the overall development of the crop. Since the germination and early seedling growth are the most vulnerable stages in the weed's life cycle, effective administration of soil applicable pesticides becomes significant throughout the growing season of the crop. Hence it is critical to prevent the early weed establishment which is advantageous throughout the season.
The mode of action for most pre-emergence herbicides is the inhibition of certain phases of cell division during the seed germination process. As the weed seed germinates, the herbicide is absorbed by the root or shoots, cell division is blocked, growth is inhibited and eventually the immature seedling dies. Emerged weeds visible at the time of application are not controlled by pre-emergence herbicides, so to be effective; they must be applied prior to weed seed germination. Hence the timing of application of such herbicides is very crucial. Pre-emergent weed killers require water to activate them and carry the chemical down to the root systems of newly sprouted weeds. These herbicides don't stop weed germination, but rather interrupt the process before a sprout pushes through soil.
Pre-emergence herbicides or early post-emergence herbicides form the base of a chemical weed control method and are used primarily to control annual grasses and certain annual broadleaf weeds. They are most effective at controlling annual grassy weeds like crabgrass, foxtail, goose grass, and barnyard grass. Fair control of annual broadleaf weeds such as purslane, spurge, and oxalis can also be expected from most pre-emergents. The length of control depends on the specific chemical being used, physical and chemical properties, and soil factors such as texture, pH and moisture, and soil temperatures.
It has been noted that there are many factors which play an important role in determining performance of an herbicide. The ability of herbicides to penetrate compacted soils varies. Also many herbicides may have a long half-life, but have poor extended residual weed control as their bioavailability to weed seeds and/or efficacy at low concentrations is low. Some are sensitive to sunlight and need to be mixed into the soil to minimize losses. Some are volatile and can be lost to evaporation, especially from wet soil. It has been observed that soil applied herbicides have a tendency to get deposited at the spraying location, which in turn limit the coverage area and availability of the active ingredient. Further, some herbicides tend to leach-out and also lead to formation of striation which again affects the efficacy of such pesticides. Water soluble herbicides get washed off site and cause environmental issues during heavy rain falls.
In addition, the successful development of any pesticide formulation depends upon the type of formulation and the auxiliary agents such as solvents, adjuvants, emulsifiers, wetting and dispersing agents which are typically required for the intended performance. Often the selection of these agents creates problems such as incompatibility of the pesticide with such components. These problems are very critical as they have a direct impact on physico-chemical stability as well as the bio-efficacy of the active ingredient.
Therefore there is a need in the art for improved soil-applied pesticide compositions which have better bioefficacy compared to the existing formulations.
Surprisingly inventors of the present invention found out that by using an adjuvant composition, the agrochemical formulations led to reduction in dosage of the active ingredient and/or better weed control.